Today's IP environments enable a wide range of automated testing.
IP networks have become a mission-critical part of just about every broadcaster's facility. Broadcasters need to monitor these networks with the same critical eye they use to monitor the rest of their video facility. This month, I will provide a high-level introduction into the topic of IP network monitoring.
Before jumping in, it might be good to look at some reasons a broadcaster might choose to monitor its IP networks. Those reasons include: establishing a baseline performance; detecting, isolating and addressing problems; identifying issues before failures occur; identifying failures that have already occurred; and, checking new IT components through acceptance testing and system commissioning. Let's look at each of these in turn:
Once you have decided that monitoring your IP network is important, and you have determined why monitoring is critical, the next obvious step is determining how to monitor your network. The easiest way to get started is to use monitoring capabilities you already have in your facility. Here are a few things to consider: router statistics, switch statistics, server statistics and workstation performance graphs. Again, let's take a look at each of these individually:
Another class of monitoring device is the network probe. While many commercial tools are available, I suggest you start with an excellent free resource — Wireshark. Wireshark is a free network sniffer or probe, which can record a series of packets and display them at a later time. It has an excellent manual, and there are many tutorials and other online resources available also.
As your familiarity with IP network monitoring grows, however, you may decide that you need to employ a full, commercial solution. There may be several reasons for this. For example, you may decide you need professional support. Or, you may require a feature or performance that is not available in free monitoring solutions. You may also decide that you need some professional video functionality that is only available in commercial solutions.
If you are moving video around in MPEG-2 on IT networks, then this may be a case where a professional monitoring tool would be useful. As you probably know, MPEG-2 can be encapsulated in UDP packets and sent over IP networks. Troubleshooting errors on IP networks that appear as glitches in MPEG-2 streams can be notoriously difficult to isolate. This is because errors can be introduced at many different levels. Is the problem present in the source video? Was the MPEG-2 stream properly configured? Is there a problem with the MPEG-2 encoder? Is there an issue with the IP transport? There are a number of places where errors could be introduced.
One tool is the FE Stream Analyzer from FE Engineering. This analyzer is specifically designed to inspect IPTV packets. The main screen gives a quick summary of critical, video-oriented measurements such as PCR jitter and video packet loss, while also displaying a number of parameters related to the compression system as well. (See Figure 1.) It will look into a multiplexed MPEG Transport Stream and allow you to pick out a particular service for analysis.
Broadcasters should be aware of another category of commercial solutions — network emulators. These devices allow you to create a clean-room network, and then degrade the network in a carefully controlled manner to determine how equipment performs under these degraded conditions.
Network emulation products allow you to select different types of network impairments and then adjust the severity of the impairments. This can be extremely useful when troubleshooting professional video equipment. Because MPEG-2 compression assigns different importance to different packets in the stream, the effect of a hit on an “I” frame will be much more pronounced than on a “B” or “P” frame. Thus, end-users may see differing effects of a particular network error depending upon where the error occurs. A network emulator will allow you to carefully control the behavior of the network, something you cannot do in the real world.
I encourage you to experiment with some of the free tools you already have in order to get familiar with the concept of network monitoring. I also encourage you to take advantage of the free trials offered by many network monitoring vendors. This can be a good way to become familiar with some of the advanced features and monitoring options that are available.
Finally, I cannot stress the importance of education enough. It is critical that professional video engineers maintain a level of expertise that allows them to understand and act upon the information made available through IP monitoring.
Brad Gilmer is president of Gilmer & Associates, executive director of the Video Services Forum and executive director of the Advanced Media Workflow Association.
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